In recent years, various types of digital microphones, characterized as such because they output audio signals in digital format, have been developed in order to overcome disadvantages inherent in analog microphones—in particular, the injection of coupling noise, and resulting decrease in signal quality, due to ambient electromagnetic energy, signal attenuations, and filtering in the signal path. Although at least some analog circuitry is eliminated by these digital microphones, thereby resulting in a less noisy output audio signal, many, if not all, of these microphones generate an intermediate analog audio signal, which must be processed by at least one analog component. Thus, such microphones are not true digital microphones in that they are incapable of transforming audible sounds directly into digital audio signals.
Almost all microphones, whether analog or digital, are mechanical in nature in that they use moving elements to create an audio signal. These elements range from long strips of aluminum hung between magnets (Ribbon Microphone), or thin film metallicized membranes suspended in a highly electrically charged cage (Condenser Microphone), to cone shaped diaphragms with wrapped wires that induce voltage when moved in a magnetic field (Dynamic Microphone). In each of these cases, the moving elements may become mechanically stressed over time, thereby reducing the working life of the microphone.
Significantly, known digital microphones, like all microphones, generate non-secure intermediate and/or output audio signals that, if accessed, can be easily transformed back into a coherent audible sound that resembles the audible sound input into the microphone. If protection of the audible sound from unauthorized third parties is desirable, a security layer can be applied to these audio signals downstream from the microphone output. For example, to secure the audio content (e.g., a song), the audio signal can be transformed into a sound file in any one of a variety of formats, such as a Windows® Audio Volume (WAV), Windows® Media Video (WMV), or Moving Picture Experts Group Layer-3 Audio (MP3) file, and protected with a digital rights management (DRM) and enforcement system, which allows only authorized persons to perform certain operations on the audio content.
There are certain situations, however, where protecting the audio content downstream from the microphone may not be sufficient. For example, in the context of a music recording studio, several audio cuts and tracks are typically generated, which are then combined or spliced into a final file version of a song or album. When the final audio version is transferred to the commercial media (e.g., compact disks), the audio content thereon can be protected with a DRM system. However, the raw content (i.e., the audio cuts and tracks) used to produce the final audio version, which may have even more commercial value than the final product, remains unprotected, and thus, can be freely distributed.
In the case where a microphone is being used as a listening device (e.g., for transmitting audio from one location to a remote location), an unauthorized third party could potentially tap into a wire downstream from the microphone, or even within the microphone itself, to access the non-secured audio signal. Also, typical microphones, whether analog or digital, have passive elements that cannot be turned off unless the microphone has a mechanical switch that can be operated (with the exception of the condenser microphone, which requires an external power supply). Thus, with few exceptions, microphones cannot be turned off remotely, and as such, will continuously be on even though their outputs may not be in use. As such, these microphones will indiscriminately generate and transmit audio signals that can potentially be accessed by an unauthorized third party.
There thus remains a need to provide a microphone that does not generate an intermediate or output audio signal that can be easily used by unauthorized persons, that can be remotely deactivated, and that comprises non-moving mechanical elements.